1. Technical Field of the Invention
The present invention relates to a gas sensor mounted on an exhaust gas pipe of an automotive engine for detecting a concentration of specified gas in measuring gases passing through the exhaust gas pipe.
2. Description of the Related Art
In related art, various attempts have heretofore been to provide gas sensors adapted to be mounted on exhaust systems of internal combustion engines such as engines of motor vehicles for measuring a concentration of specified gas such as oxygen gas contained in exhaust gases to allow a detected output to be sued for controlling an air fuel ratio. Such gas sensors include a gas sensor of an atmospheric air introduction type as disclosed in Japanese Unexamined Patent Application Publication No. 2002-131270.
Under a circumstance where the gas sensor of such a type is mounted on the exhaust pipe of the automotive engine, a distal end of the gas sensor is exposed to measuring gases with a base end of the gas sensor being exposed to atmospheric environment. In addition, the gas sensor includes a cylindrical case, fixedly secured to a base end portion of the gas sensor so as to cover a base end of a gas sensor element for detecting a gas concentration, a seal member closing an open end of the case, and a ventilation filter covering a ventilation bore through which atmospheric air is introduced. In order to provide an ease of assembling the seal member and the ventilation filter with respect to each other, the ventilation and the seal member are integrally assembled to each other by die forming.
With the gas sensor of such a related art structure, however, the seal member and the ventilation filter are bonded to each other through a mechanical connection such as mechanical clipping or caulking techniques. This results in a decrease of bonding strength of the ventilation filter and, hence, the ventilation filter has needed to be bonded in a widened joint area. This causes an edge portion of the ventilation filter to cover lead wire insertion bores formed in the seal member, causing an issue to arise in impeding the insertion of the lead wires into the seal member. This results in a difficulty in minimizing a whole of the seal member.